Various processing machines and methods for sheet processing, particularly mail processing, have been employed in the past for receiving materials from a number of sources and collating the materials, or combining them into a single packet of material. The single packet is then ready for further processing. For example, in a mail inserter system, the single packet can then be inserted into an envelope at an envelope inserting station located downstream.
In known sheet processing machines, a prime document can be typically generated or fed and additional materials can be added to the prime document as it traverses the processing machine. Typically, the packet comprises a single stack of documents, wherein the order of the documents in the stack is predetermined by the process flow of the processing machine.
Known track systems can feed documents from a series of feed stations in a synchronized manner so that a document from each feed station can be placed on top of a document from a preceding, up-stream feed station. A number of documents can be collated together to form a packet. For example, in a mail processing machine, a packet of documents can comprise one prime document, such as an address bearing document, and several attachments, such as leaflets or advertisements. The prime document can include the mailing address to which the package (e.g. envelope with packet inserted therein) is to be delivered. In such cases, collation must be performed so that when the documents are placed in a window envelope, the address will be visible through the window. This process can be accomplished by first feeding the prime document onto the track conveyor, face downwards, and adding the subsequent documents on top to form a packet which is then inserted into the envelope with the prime document facing downwards.
To improve speeds and efficiencies in sheet processing, known techniques can use a synchronous system that uses fixed pins or pusher structures of different heights and provide a method of transporting subsets of documents along a conveying path to be collated later. The fixed pins, comprising first tall pins and second short pins, alternate along a conveyor that moves them. With this system, a document which is to be placed on top of the packet must be transported by the first (shorter) set of pins in the synchronous transport. Due to the distance provided between each of the fixed pins and the speeds at which the machines run, the prime documents to be fed onto the conveying path have a short window of opportunity to be accurately and properly fed in front of the correct pin that is to push each prime document. If, for some reason, the timing of the feeding of the prime document is slightly off, the window of opportunity to feed the document may be missed. In such case, a misfeed can occur causing delays in processing. Alternatively, the feeding mechanism will have to wait until the next window of opportunity arises to feed the document in front of the correct fixed pin (short or tall) to push that document. Such waiting causes inefficiencies in processing.
In light of the above, needs exist for improved staging and processing of sheet articles, such as mailing articles particularly with regard to improving throughput and increasing efficiencies within a sheet processing machine.